Suddenly from a lumpy tussock of old grass some twenty yards in front of them, with black-tipped ears erect and long hinder limbs throwing it forward, started a hare. It bolted for a thicket of alders.

(figuratively) A dense aggregation of other things, concrete or abstract.

Hidden behind thickets of acronyms and gorse bushes of detail, a new great game is under way across the globe. Some call it geoeconomics, but it's geopolitics too. The current power play consists of an extraordinary range of countries simultaneously sitting down to negotiate big free trade and investment agreements.